Self-contained fire alarm unit



I Oct. 8, 1 957 E. EHLERS,'JR

SELF-CONTAINED FIRE ALARM UNIT Filed May 5, 1955 INVENTOR.

Ednrz'ZEZZers,

United States Patent 6 SELF-CONTAINED FEEALARM UNIT 'Edward'Ehlers, Jr.,Montclair, N. 3.

Application May 5, 1-955, Serial No. 506,296

2fClaimS. (Cl. 340-427) This invention relates 'to a self-containedfirealarm unitadapted to be mounted on a wall, ceiling or other'surface of aroom or-other-space to be served thereby.

The invention has for an object to provide a fire alarm unitcomprisingan electrically actuated alarm device, a dry battery as asource of electrical energy in circuit with said alarmdevice, saidcircuit including a thermostatic switch adapted to close in response toabnormal rise-in temperature,.such as produced by fire, and a pushbutton actuatable test switch'inshunt circuit between the battery andalarm device, these elements being all compactly contained in asinglehousing-or casing, and said casing beingso constructed as totransmitboth air borne radiant heat .and conducted heat to the thermostaticcontrol switch.

The invention has for a further object to provide a 'casingincluding arearwardly open hollow base plate upon which the elements of the firealarm unit are mounted, with the thermostatic alarm control switcharranged in such relation thereto and direct contact therewith that;heatconducted by and.:through the base plate will be rapidly transmitted tosaid switch in addition to radiant or air borne heat which enters thecasing, whereby said switchiis rendered vmorequicklyresponsive toabnormal rise oftemperature, and to thisend to provide a base platecomprising in whole or in part a highly heat conductivemetal, such ascopper.

The above andother 'objectswill be understood from a reading ofthe-following detailed description of the invention inconnection-withtheaccompanying drawings, in which:

Fig. l is a front elevational view of the self-contained fire alarm unitof this invention; Fig. 2 is a front elevational view of the same, withthe cover member of the casing removed; Fig. 3 is a longitudinalsectional view, with parts in elevation, this view being drawn on anenlarged scale; and Fig. 4 is a cross-sectional view, taken on line 44in Fig. 2, but drawn on an enlarged scale.

Referring to the drawings, in which like characters of referenceindicate corresponding parts, the reference character indicates therearwardly open hollow base plate of the fire alarm unit housing.Mounted on the external face of the base plate It), adjacent to theupper end thereof, is an electrically actuated alarm device 11, havingat its back a supporting bracket 12 which is aflixed to the base plate19 by a fastening screw 13. This alarm device may be of any well knownsound producing type, but preferably comprises an electric horn.

Mounted on the base plate 16, below the alarm device 11 is a dry battery14, which serves as the source of electrical energy by which the alarmdevice is actuated. Said battery is secured in place by retaining clipsor lugs which are struck out from the material of the base plate, so asto embrace the sides, top and bottom of the battery.

. Also mounted on the base plate 10, at its upper end, is a thermostaticswitch 16. In a preferred form there- Patented Get. 8, 1957 of, thisthermostatic switch comprises a hollow metallic casing formed byagbottom member 17 and atopmember 18, and containing a bimetallic switcharm 19, which is electrically insulated from said casing by insulation20, and a stationary contact 21, which opposes the switch arm '19 and iselectrically grounded on the casing, said casing, in turn, beingelectrically groundedon the base plate 10 (see Fig. 4).

One pole 22 of the battery 14 is connected to one pole of the alarmdevice 11 by a lead 23, and the other pole of said alarm device iselectrically grounded on the baseplate 18. The alarm actuating circuitis completed through the base plate ground to the grounded stationarycontact 21 of'the thermostatic switch, and thence, when closed byengagement of the bimetallic switch arm 19 with said stationary contact21, through said switch arm and a lead 24 connected therewith back tothe other pole 26 of the battery 14.

To enclose the above described elements of the fire alarm unit, a hollowcasing or cover member 27 is suitably attached to the base plate 16.This casing or cover member 27 is provided in its face wall, andopposite thealarm device 11 with louvered openings 28, through whichthesound of the actuated alarm device can'be unimpededly emitted. Thebottom end wall of the casing or cover member 27 is provided withadmission openings 29 through which radiant heat or air borne heat canpass upwardly into the interior of the fire alarm unit.

Suitably mounted in an through the front wall of the casing or covermember 27, preferably adjacent to the bottom end thereof, is apush-button actuable test switch 36. One pole 31 of this test switch isconnected by a lead 32 to the electrical ground provided by the baseplate 1%, and the other pole 33 of said test switch is connected bya-lead '34 to the pole as of the battery 14.

By-this arrangement the test switch 3;? is connected in a shunt circuitfrom the battery 1e through the alarm device .11 and back to saidbattery. When the push-button actuatable switch 30 is manually closed,current flows from the battery 14 through the alarm device 11 to ground,and thence back to the battery through the lead 34; thusv providing atest circuit independent of th thermostatic switch 16, by which operablecondition of thealarm device can from time to time be ascertained.

Provided in the upper end portion of the base plate It) is a key holetype opening 35, whereby to engage the fire alarm unit with a mountingscrew (not shown) which serves to support the fire alarm unit on and incontiguous contact with a wall or other srface within the room or otherspace desired to be served by said unit. When so mounted, the interiorof the hollow base plate is opposed to the supporting surface, wherebyheat emanating from said surface is confined in the hollow interior ofthe base plate, and thus concentrated therein for direct application tothe base plate so as to be conducted thereby directly to thethermostatic switch (see Fig. 3).

From the above it will now be apparent that the present inventionprovides a very compact self-contained fire alarm unit, which is welladapted for room or like service.

One of the deficiencies of thermostatically controlled electric firealarm devices, as heretofore known, is that the same depend, foroperation, practically solely upon application thereto of radiant or airborne heat generated within the building room or space served thereby.Since fires, and particularly fires starting in the lower regions of abuilding, frequently progress through the building wall interiors beforeactually entering rooms or spaces contiguous to said walls, and since,under such circumstances, generation of radiant or air borne heat withinsuch rooms or spaces is likely to be delayed, said former devices arenot well adapted to detect and give prompt warning of the existence andprogress of internal wall fires. Having this in view, the presentinvention seeks to provide a novel construction of fire alarm unit whichovercomes such deficiency, by providing said unit with a highly heatconductive path through which heat, generated within a wall on which theunit is mounted, will be quickly and directly conducted and applied tothe thermostatic switch element, even before the air temperature withinthe room rises to an alarm actuating degree. To this end, the fire alarmunit of this invention is provided with the rearwardly open hollow baseplate 10, which is effective to concentrate wall emitted heat directlyagainst the base plate, includes a metal of high heatconductivecharacteristic, such. as copper or other highly heatconductive metal.

Although the base plate may be provided solely from copper or likehighly heat conductive metal, since however such metals are relativelysoft, and therefore easily deformed it is preferred to provide the baseplate 10 with a core 36 of relatively rigid metal, such as steel, andthen plate the surfaces thereof with an external coating 37 of copper orother highly heat conductive metal, which coating provides the baseplate with. the desired highly conductive heat path.

The casing 17 18 of the thermostatic switch 16 is mounted in directcontact with the heat conductive copper or like coating 37 of the baseplate it), and is held in place by retaining clips or lugs 25 which arestruck up out of the base plate, so that the heat conductive copper orlike coated portions of said clips or lugs contact the opposite sides ofthe switch casing 17-18, with enhanced conducted heat transfer effect.Heat emanating from a wall upon which the fire alarm unit is mountedwill be confined in the base plate chamber and, will be quicklytransferred directly to the base plate It), and thereupon will berapidly conducted to the thermostatic switch 16 by way of the highlyheat conductive path provided by the copper or like coating 37 of saidbase plate.

Radiant or air borne heat can enter the interior of the casing or covermember 27 through its bottom openings 29, so as to rise therein forcontact with the thermostatic switch 36. Such entering radiant or airborne heat also contacts and is transferred to the copper or like coatin37 of the base plate 1%, so as to be rapidly conducted thereby to thethermostatic switch in addition to the direct contact of the radiant orair borne heat with 7 the latter, thereby assuring operation of saidswitch in response to heat within a minimum interval of time.

Having now described my invention, I claim:

1. A self-contained fire alarm unit comprising a rearwardly open hollowbase plate providing a chamber to confine heat emanating from a surfacecontiguous to whichthe unit is mounted, whereby to concentrate said heatin direct contact with the base plate for conduction thereby, anelectrically actuated alarm device mounted on said base plate, a drybattery mounted on said base plate, a thermostatic switch, a heatconductive support for said thermostatic switch also mounted on saidbase plate, and a circuit connecting said alarm device and thermostaticswitch in series with said battery, an enclosing hollow cover supportedby said base plate, said cover having openings therein to admit radiantand air borne heat for contact with said thermostatic switch, and saidbase plate including a coating of highly heat conductivernetal, such ascopper, said support of the thermostatic switch being disposed in directcontact with said heat conductive metal coating of the base plate forreception of conducted heat therefrom.

2. A self-contained fire alarm unitcomprising a rearwardly open hollowbase-plate having a rigid metallic core plated with an external coatingof a highly heat conductive metal, such as copper, said base plateproviding a chamber to confine heat emanating from a surface contiguousto which the unit is mounted,'whereby to concentrate said heat in directcontact with the base plate for conduction thereby an electricallyactuated alarm device mounted on said base plate, a dry battery mountedon said base plate, a thermostatic switch, a heat conductive casingenclosing said thermostatic switch, said casing being mounted on saidbase plate in direct contact with the heat conductive coating thereoffor reception of conducted heat therefrom, a circuit connecting saidalarm device and thermostatic switch in series with said battery, and ahollow cover supported by said base plate, said cover having openingstherein to admit radiant heat and air borne heat for contact with thethermostatic switch.

References Cited in the file of this patent UNITED STATES PATENTS CufaloMay 1, 1951

